Taylor Swift: 65,000 people registered to vote in the 24 hours after the singer’s Instagram post. Photograph: Matt Winkelmeyer/TAS18/Getty

The US voter registration service has experienced a spike in numbers after Taylor Swift – long silent on partisan issues – expressed her support for two Democratic candidates and encouraged her 112 million Instagram followers to register to vote in time for next month’s US midterm elections.

Swift focused her post on the United States Senate race in Tennessee, where she is registered to vote. She wrote that although she had previously voted for women in office, she felt unable to support the Republican senate candidate, Marsha Blackburn. “Her voting record in Congress appalls and terrifies me,” she said, adding that she would be voting for the Democrat candidates Phil Bredesen, for the Senate, and Jim Cooper, for the House of Representatives.

Of the 5,183 voter registrations in Tennessee this month, at least 2,144 occurred after Swift posted her statement on Instagram, Guthrie says. There were 2,811 new Tennessee voter registrations in September.

In her post Swift affirmed her commitment to the fight for LGBTQ rights and described the “systemic racism” towards people of colour in the US as “terrifying, sickening and prevalent”. She encouraged her young fans to find out about their local candidates and “vote based on who most closely represents your values”.

Her statement drew criticism from Donald Trump. On Monday the US president told reporters: “Marsha Blackburn is doing a very good job in Tennessee. She’s leading now substantially, which she should. She’s a tremendous woman. I’m sure Taylor Swift doesn’t know anything about her. Let’s say that I like Taylor’s music about 25 per cent less now, okay?”

Bredesen thanked Swift, tweeting: “I’m honoured to have your support and that of so many Tennesseans who are ready to put aside the partisan shouting and get things done. We’re ready for it.”

Swift is performing her song I Did Something Bad at tonight’s American Music Awards in Los Angeles. She has made few appearances at awards ceremonies since the release of her 2017 album, Reputation. She is nominated in four categories: artist of the year, favourite pop/rock artist, favourite pop/rock album (for Reputation) and tour of the year, for the Reputation stadium tour. –Guardian